Optical lens set

ABSTRACT

An optical lens set includes a first lens element of an object-side surface with a convex portion in a vicinity of an optical axis, a second lens element of an image-side surface with a concave portion in a vicinity of its periphery and a sixth lens element of an image-side surface with a convex portion in a vicinity of its periphery. T 5 min is the minimal distance from the object-side surface of the fifth lens element to the image-side surface of the fifth lens element and the fifth lens element has a fifth lens element thickness T 5  along the optical axis to satisfy T 5 min/T 5 ≦0.6.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Chinese patent application No.201610804274.5, filed on 2016 Sep. 6, and from Chinese patentapplication No. 201610635125.0, filed on 2016 Aug. 5, the contents ofwhich are hereby incorporated by reference in their entirety for allpurposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens set.Specifically speaking, the present invention is directed to a shorteroptical imaging lens set of six lens elements for use in mobile phones,in cameras, in tablet personal computers, in in-car cameras, or inpersonal digital assistants (PDA).

2. Description of the Prior Art

In recent years, the popularity of mobile phones and digital camerasmakes the sizes of various portable electronic products reduce quickly,and so does those of the photography modules. With the development andshrinkage of a charge coupled device (CCD) or a complementary metaloxide semiconductor element (CMOS), the optical imaging lens setinstalled in the photography module shrinks as well to meet the demands.The current trend of research is to develop an optical imaging lens setof a shorter length with uncompromised good quality. However, good andnecessary optical properties, such as the system aberration improvement,as well as production cost and production feasibility should be takeninto consideration, too.

As far as an optical imaging lens set of six lens elements is concerned,the distance between a first object-side surface of the first lenselement to an image plane, namely the total length TTL of an opticalimaging lens set, is longer to be adversely affect the shrinkage ofmobile phones and digital cameras. Accordingly, an optical imaging lensset of good imaging quality, good luminous flux and reduced TTL is stillneeded.

SUMMARY OF THE INVENTION

In light of the above, the present invention proposes an optical imaginglens set that is smaller, has a low production cost, has an enlargedhalf of field of view, has a high resolution and has high image quality.The optical imaging lens set of six lens elements of the presentinvention from an object side toward an image side in order along anoptical axis has a first lens element, a second lens element, a thirdlens element, a fourth lens element, a fifth lens element and a sixthlens element. Each lens element has an object-side surface facing towardan object side as well as an image-side surface facing toward an imageside. The optical imaging lens set exclusively has the first lenselement, the second lens element, the third lens element, the fourthlens element, the fifth lens element and the sixth lens element withrefractive power.

The first lens element has an object-side surface with a convex portionin a vicinity of the optical axis. The second lens element has animage-side surface with a concave portion in a vicinity of itsperiphery. The sixth lens element has an image-side surface with aconvex portion in a vicinity of its periphery.

T₅min is the minimal distance from the object-side surface of the fifthlens element to the image-side surface of the fifth lens element and thefifth lens element has a fifth lens element thickness T₅ along theoptical axis to satisfy T₅min/T₅≦0.6.

In the optical imaging lens set of six lens elements of the presentinvention, ALT is the total thickness of all six lens elements, an airgap G₃₄ between the third lens element and the fourth lens element alongthe optical axis and an air gap G₅₆ between the fifth lens element andthe sixth lens element along the optical axis to satisfyALT/(G₃₄+G₅₆)≦17.5.

In the optical imaging lens set of six lens elements of the presentinvention, EFL is the effective focal length of the optical imaging lensset and the third lens element has a third lens element thickness T₃along the optical axis to satisfy EFL/T₃≦18.5.

In the optical imaging lens set of six lens elements of the presentinvention, the fourth lens element has a fourth lens element thicknessT₄ along the optical axis to satisfy T₅/T₄≦3.5.

In the optical imaging lens set of six lens elements of the presentinvention, the second lens element has a second lens element thicknessT₂ along the optical axis to satisfy ALT/T₂≦13.5.

In the optical imaging lens set of six lens elements of the presentinvention, the sum of all air gaps AAG between each lens elements fromthe first lens element to the sixth lens element along the optical axisto satisfy AAG/T₃≧1.8.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₁₂ between the first lens element and the secondlens element along the optical axis and an air gap G₂₃ between thesecond lens element and the third lens element along the optical axis tosatisfy EFL/(G₁₂+G₂₃)≦13.

In the optical imaging lens set of six lens elements of the presentinvention, the first lens element has a first lens element thickness T₁along the optical axis to satisfy T₁/T₂≦3.6.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₄₅ between the fourth lens element and the fifthlens element along the optical axis to satisfy (G₂₃+G₄₅)/T₂≦4.

The optical imaging lens set of six lens elements of the presentinvention satisfies T₅/(G₃₄+G₄₅)≦3.5.

In the optical imaging lens set of six lens elements of the presentinvention, the sixth lens element has a sixth lens element thickness T₆along the optical axis to satisfy ALT/(T₂+T₆)≦4.4.

The optical imaging lens set of six lens elements of the presentinvention satisfies EFL/(T₃+T₆)≦6.5.

In the optical imaging lens set of six lens elements of the presentinvention, the fifth lens element has an image-side surface with aconvex portion in a vicinity of the optical axis.

The optical imaging lens set of six lens elements of the presentinvention satisfies AAG/(T₂+T₃)≦3.5.

The optical imaging lens set of six lens elements of the presentinvention satisfies T₁/T₃≧1.

The optical imaging lens set of six lens elements of the presentinvention satisfies (G₂₃+G₅₆)/T₂≦3.6.

The optical imaging lens set of six lens elements of the presentinvention satisfies EFL/(T₄+T₆)≦5.7.

The optical imaging lens set of six lens elements of the presentinvention satisfies ALT/(G₂₃+G₃₄)≦8.

The optical imaging lens set of six lens elements of the presentinvention satisfies EFL/(T₁+T₃)≦5.

The optical imaging lens set of six lens elements of the presentinvention satisfies T₅/(G₁₂+G₂₃)≦1.8.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrates the methods for determining the surface shapes andfor determining one region is a region in a vicinity of the optical axisor the region in a vicinity of its circular periphery of one lenselement.

FIG. 6 illustrates a first example of the optical imaging lens set ofthe present invention.

FIG. 7A illustrates the longitudinal spherical aberration on the imageplane of the first example.

FIG. 7B illustrates the astigmatic aberration on the sagittal directionof the first example.

FIG. 7C illustrates the astigmatic aberration on the tangentialdirection of the first example.

FIG. 7D illustrates the distortion aberration of the first example.

FIG. 8 illustrates a second example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the imageplane of the second example.

FIG. 9B illustrates the astigmatic aberration on the sagittal directionof the second example.

FIG. 9C illustrates the astigmatic aberration on the tangentialdirection of the second example.

FIG. 9D illustrates the distortion aberration of the second example.

FIG. 10 illustrates a third example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the imageplane of the third example.

FIG. 11B illustrates the astigmatic aberration on the sagittal directionof the third example.

FIG. 11C illustrates the astigmatic aberration on the tangentialdirection of the third example.

FIG. 11D illustrates the distortion aberration of the third example.

FIG. 12 illustrates a fourth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the imageplane of the fourth example.

FIG. 13B illustrates the astigmatic aberration on the sagittal directionof the fourth example.

FIG. 13C illustrates the astigmatic aberration on the tangentialdirection of the fourth example.

FIG. 13D illustrates the distortion aberration of the fourth example.

FIG. 14 illustrates a fifth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the imageplane of the fifth example.

FIG. 15B illustrates the astigmatic aberration on the sagittal directionof the fifth example.

FIG. 15C illustrates the astigmatic aberration on the tangentialdirection of the fifth example.

FIG. 15D illustrates the distortion aberration of the fifth example.

FIG. 16 illustrates a sixth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the imageplane of the sixth example.

FIG. 17B illustrates the astigmatic aberration on the sagittal directionof the sixth example.

FIG. 17C illustrates the astigmatic aberration on the tangentialdirection of the sixth example.

FIG. 17D illustrates the distortion aberration of the sixth example.

FIG. 18 illustrates a seventh example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the imageplane of the seventh example.

FIG. 19B illustrates the astigmatic aberration on the sagittal directionof the seventh example.

FIG. 19C illustrates the astigmatic aberration on the tangentialdirection of the seventh example.

FIG. 19D illustrates the distortion aberration of the seventh example.

FIG. 20 illustrates an eighth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 21A illustrates the longitudinal spherical aberration on the imageplane of the eighth example.

FIG. 21B illustrates the astigmatic aberration on the sagittal directionof the eighth example.

FIG. 21C illustrates the astigmatic aberration on the tangentialdirection of the eighth example.

FIG. 21D illustrates the distortion aberration of the eighth example.

FIG. 22 shows the optical data of the first example of the opticalimaging lens set.

FIG. 23 shows the aspheric surface data of the first example.

FIG. 24 shows the optical data of the second example of the opticalimaging lens set.

FIG. 25 shows the aspheric surface data of the second example.

FIG. 26 shows the optical data of the third example of the opticalimaging lens set.

FIG. 27 shows the aspheric surface data of the third example.

FIG. 28 shows the optical data of the fourth example of the opticalimaging lens set.

FIG. 29 shows the aspheric surface data of the fourth example.

FIG. 30 shows the optical data of the fifth example of the opticalimaging lens set.

FIG. 31 shows the aspheric surface data of the fifth example.

FIG. 32 shows the optical data of the sixth example of the opticalimaging lens set.

FIG. 33 shows the aspheric surface data of the sixth example.

FIG. 34 shows the optical data of the seventh example of the opticalimaging lens set.

FIG. 35 shows the aspheric surface data of the seventh example.

FIG. 36 shows the optical data of the eighth example of the opticalimaging lens set.

FIG. 37 shows the aspheric surface data of the eighth example.

FIG. 38 shows some important ratios in the examples.

DETAILED DESCRIPTION

Before the detailed description of the present invention, the firstthing to be noticed is that in the present invention, similar (notnecessarily identical) elements are labeled as the same numeralreferences. In the entire present specification, “a certain lens elementhas negative/positive refractive power” refers to the part in a vicinityof the optical axis of the lens element has negative/positive refractivepower calculated by Gaussian optical theory. An object-side/image-sidesurface refers to the region which allows imaging light passing through,in the drawing, imaging light includes Lc (chief ray) and Lm (marginalray). As shown in FIG. 1, the optical axis is “I” and the lens elementis symmetrical with respect to the optical axis I. The region A thatnear the optical axis and for light to pass through is the region in avicinity of the optical axis, and the region C that the marginal raypassing through is the region in a vicinity of a certain lens element'scircular periphery. In addition, the lens element may include anextension part E for the lens element to be installed in an opticalimaging lens set (that is the region outside the region C perpendicularto the optical axis). Ideally speaking, no light would pass through theextension part, and the actual structure and shape of the extension partis not limited to this and may have other variations. For the reason ofsimplicity, the extension part is not illustrated in the followingexamples. More, precisely, the method for determining the surface shapesor the region in a vicinity of the optical axis, the region in avicinity of its circular periphery and other regions is described in thefollowing paragraphs:

1. FIG. 1 is a radial cross-sectional view of a lens element. Beforedetermining boundaries of those aforesaid portions, two referentialpoints should be defined first, middle point and conversion point. Themiddle point of a surface of a lens element is a point of intersectionof that surface and the optical axis. The conversion point is a point ona surface of a lens element, where the tangent line of that point isperpendicular to the optical axis. Additionally, if multiple conversionpoints appear on one single surface, then these conversion points aresequentially named along the radial direction of the surface withnumbers starting from the first conversion point. For instance, thefirst conversion point (closest one to the optical axis), the secondconversion point, and the N^(th) conversion point (farthest one to theoptical axis within the scope of the clear aperture of the surface). Theportion of a surface of the lens element between the middle point andthe first conversion point is defined as the portion in a vicinity ofthe optical axis. The portion located radially outside of the N^(th)conversion point (but still within the scope of the clear aperture) isdefined as the portion in a vicinity of a periphery of the lens element.In some embodiments, there are other portions existing between theportion in a vicinity of the optical axis and the portion in a vicinityof a periphery of the lens element; the numbers of portions depend onthe numbers of the conversion point(s). In addition, the radius of theclear aperture (or a so-called effective radius) of a surface is definedas the radial distance from the optical axis I to a point ofintersection of the marginal ray Lm and the surface of the lens element.2. Referring to FIG. 2, determining the shape of a portion is convex orconcave depends on whether a collimated ray passing through that portionconverges or diverges. That is, while applying a collimated ray to aportion to be determined in terms of shape, the collimated ray passingthrough that portion will be bended and the ray itself or its extensionline will eventually meet the optical axis. The shape of that portioncan be determined by whether the ray or its extension line meets(intersects) the optical axis (focal point) at the object-side orimage-side. For instance, if the ray itself intersects the optical axisat the image side of the lens element after passing through a portion,i.e. the focal point of this ray is at the image side (see point R inFIG. 2), the portion will be determined as having a convex shape. On thecontrary, if the ray diverges after passing through a portion, theextension line of the ray intersects the optical axis at the object sideof the lens element, i.e. the focal point of the ray is at the objectside (see point M in FIG. 2), that portion will be determined as havinga concave shape. Therefore, referring to FIG. 2, the portion between themiddle point and the first conversion point has a convex shape, theportion located radially outside of the first conversion point has aconcave shape, and the first conversion point is the point where theportion having a convex shape changes to the portion having a concaveshape, namely the border of two adjacent portions. Alternatively, thereis another common way for a person with ordinary skill in the art totell whether a portion in a vicinity of the optical axis has a convex orconcave shape by referring to the sign of an “R” value, which is the(paraxial) radius of curvature of a lens surface. The R value iscommonly used in conventional optical design software such as Zemax andCodeV. The R value usually appears in the lens data sheet in thesoftware. For an object-side surface, positive R means that theobject-side surface is convex, and negative R means that the object-sidesurface is concave. Conversely, for an image-side surface, positive Rmeans that the image-side surface is concave, and negative R means thatthe image-side surface is convex. The result found by using this methodshould be consistent as by using the other way mentioned above, whichdetermines surface shapes by referring to whether the focal point of acollimated ray is at the object side or the image side.3. For none conversion point cases, the portion in a vicinity of theoptical axis is defined as the portion between 0˜50% of the effectiveradius (radius of the clear aperture) of the surface, whereas theportion in a vicinity of a periphery of the lens element is defined asthe portion between 50˜100% of effective radius (radius of the clearaperture) of the surface.

Referring to the first example depicted in FIG. 3, only one conversionpoint, namely a first conversion point, appears within the clearaperture of the image-side surface of the lens element. Portion I is aportion in a vicinity of the optical axis, and portion II is a portionin a vicinity of a periphery of the lens element. The portion in avicinity of the optical axis is determined as having a concave surfacedue to the R value at the image-side surface of the lens element ispositive. The shape of the portion in a vicinity of a periphery of thelens element is different from that of the radially inner adjacentportion, i.e. the shape of the portion in a vicinity of a periphery ofthe lens element is different from the shape of the portion in avicinity of the optical axis; the portion in a vicinity of a peripheryof the lens element has a convex shape.

Referring to the second example depicted in FIG. 4, a first conversionpoint and a second conversion point exist on the object-side surface(within the clear aperture) of a lens element. In which portion I is theportion in a vicinity of the optical axis, and portion III is theportion in a vicinity of a periphery of the lens element. The portion ina vicinity of the optical axis has a convex shape because the R value atthe object-side surface of the lens element is positive. The portion ina vicinity of a periphery of the lens element (portion III) has a convexshape. What is more, there is another portion having a concave shapeexisting between the first and second conversion point (portion II).

Referring to a third example depicted in FIG. 5, no conversion pointexists on the object-side surface of the lens element. In this case, theportion between 0˜50% of the effective radius (radius of the clearaperture) is determined as the portion in a vicinity of the opticalaxis, and the portion between 50˜100% of the effective radius isdetermined as the portion in a vicinity of a periphery of the lenselement. The portion in a vicinity of the optical axis of theobject-side surface of the lens element is determined as having a convexshape due to its positive R value, and the portion in a vicinity of aperiphery of the lens element is determined as having a convex shape aswell.

As shown in FIG. 6, the optical imaging lens set 1 of six lens elementsof the present invention, sequentially located from an object side 2(where an object is located) to an image side 3 along an optical axis 4,has an aperture stop (ape. stop) 80, a first lens element 10, a secondlens element 20, a third lens element 30, a fourth lens element 40, afifth lens element 50, a sixth lens element 60, a filter 70 and an imageplane 71. Generally speaking, the first lens element 10, the second lenselement 20, the third lens element 30, the fourth lens element 40, thefifth lens element 50 and the sixth lens element 60 may be made of atransparent plastic material but the present invention is not limited tothis, and each has an appropriate refractive power. There areexclusively six lens elements, which means the first lens element 10,the second lens element 20, the third lens element 30, the fourth lenselement 40, the fifth lens element 50 and the sixth lens element 60,with refractive power in the optical imaging lens set 1 of the presentinvention. The optical axis 4 is the optical axis of the entire opticalimaging lens set 1, and the optical axis of each of the lens elementscoincides with the optical axis of the optical imaging lens set 1.

Furthermore, the optical imaging lens set 1 includes an aperture stop(ape. stop) 80 disposed in an appropriate position. In FIG. 6, theaperture stop 80 is disposed between the object side 2 and the firstlens element 10. When light emitted or reflected by an object (notshown) which is located at the object side 2 enters the optical imaginglens set 1 of the present invention, it forms a clear and sharp image onthe image plane 71 at the image side 3 after passing through theaperture stop 80, the first lens element 10, the second lens element 20,the third lens element 30, the fourth lens element 40, the fifth lenselement 50, the sixth lens element 60 and the filter 70. In oneembodiments of the present invention, the optional filter 70 may be afilter of various suitable functions, for example, the filter 70 may bean infrared cut filter (IR cut filter), placed between the image-sidesurface 62 of the sixth lens element 60 and the image plane 71.

Each lens element in the optical imaging lens set 1 of the presentinvention has an object-side surface facing toward the object side 2 aswell as an image-side surface facing toward the image side 3. Forexample, the first lens element 10 has a first object-side surface 11and a first image-side surface 12; the second lens element 20 has asecond object-side surface 21 and a second image-side surface 22; thethird lens element 30 has a third object-side surface 31 and a thirdimage-side surface 32; the fourth lens element 40 has a fourthobject-side surface 41 and a fourth image-side surface 42; the fifthlens element 50 has a fifth object-side surface 51 and a fifthimage-side surface 52; the sixth lens element 60 has a sixth object-sidesurface 61 and a sixth image-side surface 62. In addition, eachobject-side surface and image-side surface in the optical imaging lensset 1 of the present invention has a part (or portion) in a vicinity ofits circular periphery (circular periphery part) away from the opticalaxis 4 as well as a part in a vicinity of the optical axis (optical axispart) close to the optical axis 4.

Each lens element in the optical imaging lens set 1 of the presentinvention further has a central thickness T on the optical axis 4. Forexample, the first lens element 10 has a first lens element thicknessT₁, the second lens element 20 has a second lens element thickness T₂,the third lens element 30 has a third lens element thickness T₃, thefourth lens element 40 has a fourth lens element thickness T₄, the fifthlens element 50 has a fifth lens element thickness T₅, the sixth lenselement 60 has a sixth lens element thickness T₆. Therefore, the totalthickness of all the lens elements in the optical imaging lens set 1along the optical axis 4 is ALT=T₁+T₂+T₃+T₄+T₅+T₆.

The present invention in particular indicates that the fifth lenselement 50 has a minimal lens thickness T₅min. T₅min is the minimaldistance from a percent point, namely an object-side percent point, onthe object-side surface 51 of the fifth lens element 50 to anotherpercent point, namely an image-side percent point, on the image-sidesurface 52 of the fifth lens element 50. The effective radii of both theobject-side surface 51 of the fifth lens element 50 and the image-sidesurface 52 of the fifth lens element 50 are equally divided into 100percent points. Each percent point on each surface is respectivelycalled an O^(th) object-side percent point and an I^(th) image-sidepercent point so there are 100 object-side percent points on theobject-side surface 51 in total and 100 image-side percent points on theimage-side surface 52 in total. The coordinate (O^(th), I^(th)) is usedto denote T₅min.

For example, the first object-side percent point is the 0^(th) percentpoint (the coordinate) at the optical axis 4, the 51^(th) object-sidepercent point is (50) at the midpoint and the last object-side percentpoint is (100) at its periphery. Similarly, the first image-side percentpoint is the 0^(th) percent point (the coordinate) at the optical axis4, the 51^(th) image-side percent point is (50) at the midpoint and thelast image-side percent point is (100) at its periphery.

In addition, between two adjacent lens elements in the optical imaginglens set 1 of the present invention there is an air gap along theoptical axis 4. For example, an air gap G₁₂ is disposed between thefirst lens element 10 and the second lens element 20, an air gap G₂₃ isdisposed between the second lens element 20 and the third lens element30, an air gap G₃₄ is disposed between the third lens element 30 and thefourth lens element 40, an air gap G₄₅ is disposed between the fourthlens element 40 and the fifth lens element 50 as well as an air gap G₅₆is disposed between the fifth lens element 50 and the sixth lens element60. Therefore, the sum of total five air gaps between adjacent lenselements from the first lens element 10 to the sixth lens element 60along the optical axis 4 is AAG=G₁₂+G₂₃+G₃₄+G₄₅+G₅₆.

In addition, the distance between the first object-side surface 11 ofthe first lens element 10 to the image plane 71, namely the total lengthof the optical imaging lens set along the optical axis 4 is TTL; theeffective focal length of the optical imaging lens set is EFL; thedistance between the sixth image-side surface 62 of the sixth lenselement 60 to the image plane 71 along the optical axis 4 is BFL.

Furthermore, the focal length of the first lens element 10 is f1; thefocal length of the second lens element 20 is f2; the focal length ofthe third lens element 30 is f3; the focal length of the fourth lenselement 40 is f4; the focal length of the fifth lens element 50 is f5;the focal length of the sixth lens element 60 is f6; the refractiveindex of the first lens element 10 is n1; the refractive index of thesecond lens element 20 is n2; the refractive index of the third lenselement 30 is n3; the refractive index of the fourth lens element 40 isn4; the refractive index of the fifth lens element 50 is n5; therefractive index of the sixth lens element 60 is n6; the Abbe number ofthe first lens element 10 is υ1; the Abbe number of the second lenselement 20 is υ2; the Abbe number of the third lens element 30 is υ3;and the Abbe number of the fourth lens element 40 is υ4; the Abbe numberof the fifth lens element 50 is υ5; and the Abbe number of the sixthlens element 60 is υ6.

First Example

Please refer to FIG. 6 which illustrates the first example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 7A for the longitudinal spherical aberration on the image plane 71of the first example; please refer to FIG. 7B for the astigmatic fieldaberration on the sagittal direction; please refer to FIG. 7C for theastigmatic field aberration on the tangential direction, and pleaserefer to FIG. 7D for the distortion aberration. The Y axis of thespherical aberration in each example is “field of view” for 1.0. The Yaxis of the astigmatic field and the distortion in each example standsfor “image height”, which is 3.5 mm.

The optical imaging lens set 1 of the first example has six lenselements 10 to 60 with refractive power. The optical imaging lens set 1also has a filter 70, an aperture stop 80, and an image plane 71. Theaperture stop 80 is provided between the object side 2 and the firstlens element 10. The filter 70 may be used for preventing specificwavelength light (such as the infrared light) reaching the image planeto adversely affect the imaging quality.

The first lens element 10 has positive refractive power. The firstobject-side surface 11 facing toward the object side 2 has a convex part13 in the vicinity of the optical axis and a convex part 14 in avicinity of its circular periphery. The first image-side surface 12facing toward the image side 3 has a concave part 16 in the vicinity ofthe optical axis and a convex part 17 in a vicinity of its circularperiphery. Besides, both the first object-side surface 11 and the firstimage-side 12 of the first lens element 10 are aspherical surfaces.

The second lens element 20 has negative refractive power. The secondobject-side surface 21 facing toward the object side 2 has a convex part23 in the vicinity of the optical axis and a convex part 24 in avicinity of its circular periphery. The second image-side surface 22facing toward the image side 3 has a concave part 26 in the vicinity ofthe optical axis and a concave part 27 in a vicinity of its circularperiphery. Both the second object-side surface 21 and the secondimage-side 22 of the second lens element 20 are aspherical surfaces.

The third lens element 30 has negative refractive power. The thirdobject-side surface 31 facing toward the object side 2 has a convex part33 in the vicinity of the optical axis and a concave part 34 in avicinity of its circular periphery. The third image-side surface 32facing toward the image side 3 has a concave part 36 in the vicinity ofthe optical axis and a convex part 37 in a vicinity of its circularperiphery. Both the third object-side surface 31 and the thirdimage-side 32 of the third lens element 30 are aspherical surfaces.

The fourth lens element 40 has negative refractive power. The fourthobject-side surface 41 facing toward the object side 2 has a convex part43 in the vicinity of the optical axis and a concave part 44 in avicinity of its circular periphery. The fourth image-side surface 42facing toward the image side 3 has a concave part 46 in the vicinity ofthe optical axis and a convex part 47 in a vicinity of its circularperiphery. Both the fourth object-side surface 41 and the fourthimage-side 42 of the fourth lens element 40 are aspherical surfaces.

The fifth lens element 50 has positive refractive power. The fifthobject-side surface 51 facing toward the object side 2 has a concavepart 53 in the vicinity of the optical axis and a concave part 54 in avicinity of its circular periphery. The fifth image-side surface 52facing toward the image side 3 has a convex part 56 in the vicinity ofthe optical axis and a convex part 57 in a vicinity of its circularperiphery. Both the fifth object-side surface 51 and the fifthimage-side 52 of the fifth lens element 50 are aspherical surfaces.

The sixth lens element 60 has negative refractive power. The sixthobject-side surface 61 facing toward the object side 2 has a concavepart 63 in the vicinity of the optical axis and a convex part 64 in avicinity of its circular periphery. The sixth image-side surface 62facing toward the image side 3 has a concave part 66 in the vicinity ofthe optical axis and a convex part 67 in a vicinity of its circularperiphery. Both the sixth object-side surface 61 and the sixthimage-side 62 of the sixth lens element 60 are aspherical surfaces. Thefilter 70 is disposed between the sixth image-side 62 of the sixth lenselement 60 and the image plane 71.

In the first lens element 10, the second lens element 20, the third lenselement 30, the fourth lens element 40, the fifth lens element 50 andthe sixth lens element 60 of the optical imaging lens element 1 of thepresent invention, there are 12 surfaces, such as the object-sidesurfaces 11/21/31/41/51/61 and the image-side surfaces12/22/32/42/52/62. If a surface is aspherical, these asphericcoefficients are defined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}/( {1 + \sqrt{1 - {( {1 + K} )\frac{Y^{2}}{R^{2}}}}} )} + {\sum\limits_{i = 1}^{n}{a_{2i}Y^{2i}}}}$

In which:R represents the curvature radius of the lens element surface;Z represents the depth of an aspherical surface (the perpendiculardistance between the point of the aspherical surface at a distance Yfrom the optical axis and the tangent plane of the vertex on the opticalaxis of the aspherical surface);Y represents a vertical distance from a point on the aspherical surfaceto the optical axis;K is a conic constant;a_(2i) is the aspheric coefficient of the 2i^(th) order.

The optical data of the first example of the optical imaging lens set 1are shown in FIG. 22 while the aspheric surface data are shown in FIG.23. In the present examples of the optical imaging lens set, thef-number of the entire optical lens element system is Fno, EFL is theeffective focal length, HFOV stands for the half field of view which ishalf of the field of view of the entire optical lens element system, andthe unit for the curvature radius, the thickness and the focal length isin millimeters (mm). TTL is 6.010 mm. Fno is 1.79. The image height is3.5 mm. HFOV is 35.913 degrees. T₅min (95, 88) is 0.412 mm.

Second Example

Please refer to FIG. 8 which illustrates the second example of theoptical imaging lens set 1 of the present invention. It is noted thatfrom the second example to the following examples, in order to simplifythe figures, only the components different from what the first examplehas, and the basic lens elements will be labeled in figures. Othercomponents that are the same as what the first example has, such as theobject-side surface, the image-side surface, the part in a vicinity ofthe optical axis and the part in a vicinity of its circular peripherywill be omitted in the following examples. Please refer to FIG. 9A forthe longitudinal spherical aberration on the image plane 71 of thesecond example, please refer to FIG. 9B for the astigmatic aberration onthe sagittal direction, please refer to FIG. 9C for the astigmaticaberration on the tangential direction, and please refer to FIG. 9D forthe distortion aberration. The components in the second example aresimilar to those in the first example, but the optical data such as thecurvature radius, the refractive power, the lens thickness, the lensfocal length, the aspheric surface or the back focal length in thisexample are different from the optical data in the first example, and inthis example, the sixth object-side surface 61 has a concave 64 part ina vicinity of its circular periphery.

The optical data of the second example of the optical imaging lens setare shown in FIG. 24 while the aspheric surface data are shown in FIG.25. TTL is 5.944 mm. Fno is 1.78. The image height is 3.5 mm. HFOV is36.134 degrees. T₅min (83, 79) is 0.443 mm. In particular, 1) the TTL ofthe second example is shorter than that of the first example of thepresent invention, 2) the HFOV of the second example is better than thatof the first example of the present invention, and 3) the Fno of thesecond example is better than that of the first example of the presentinvention.

Third Example

Please refer to FIG. 10 which illustrates the third example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 11A for the longitudinal spherical aberration on the image plane 71of the third example; please refer to FIG. 11B for the astigmaticaberration on the sagittal direction; please refer to FIG. 11C for theastigmatic aberration on the tangential direction, and please refer toFIG. 11D for the distortion aberration. The components in the thirdexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the sixth object-side surface 61 has a concave 64part in a vicinity of its circular periphery.

The optical data of the third example of the optical imaging lens setare shown in FIG. 26 while the aspheric surface data are shown in FIG.27. TTL is 5.965 mm. Fno is 1.78. The image height is 3.5 mm. HFOV is36.147 degrees. T₅min (84, 80) is 0.430 mm. In particular, 1) the TTL ofthe third example is shorter than that of the first example of thepresent invention, 2) the HFOV of the third example is better than thatof the first example of the present invention, and 3) the Fno of thethird example is better than that of the first example of the presentinvention so the yield would be better.

Fourth Example

Please refer to FIG. 12 which illustrates the fourth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 13A for the longitudinal spherical aberration on the image plane 71of the fourth example; please refer to FIG. 13B for the astigmaticaberration on the sagittal direction; please refer to FIG. 13C for theastigmatic aberration on the tangential direction, and please refer toFIG. 13D for the distortion aberration. The components in the fourthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example.

The optical data of the fourth example of the optical imaging lens setare shown in FIG. 28 while the aspheric surface data are shown in FIG.29. TTL is 5.955 mm. Fno is 1.80. The image height is 3.5 mm. HFOV is35.807 degrees. T₅min (92, 86) is 0.327 mm. In particular, the TTL ofthe fourth example is shorter than that of the first example of thepresent invention.

Fifth Example

Please refer to FIG. 14 which illustrates the fifth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 15A for the longitudinal spherical aberration on the image plane 71of the fifth example; please refer to FIG. 15B for the astigmaticaberration on the sagittal direction; please refer to FIG. 15C for theastigmatic aberration on the tangential direction, and please refer toFIG. 15D for the distortion aberration. The components in the fifthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example.

The optical data of the fifth example of the optical imaging lens setare shown in FIG. 30 while the aspheric surface data are shown in FIG.31. TTL is 5.871 mm. Fno is 1.74. The image height is 3.5 mm. HFOV is36.753 degrees. T₅min (86, 83) is 0.313 mm. In particular, 1) the TTL ofthe fifth example is shorter than that of the first example of thepresent invention, 2) the HFOV of the fifth example is better than thatof the first example of the present invention, and 3) the Fno of thefifth example is better than that of the first example of the presentinvention and the yield would be better.

Sixth Example

Please refer to FIG. 16 which illustrates the sixth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 17A for the longitudinal spherical aberration on the image plane 71of the sixth example; please refer to FIG. 17B for the astigmaticaberration on the sagittal direction; please refer to FIG. 17C for theastigmatic aberration on the tangential direction, and please refer toFIG. 17D for the distortion aberration. The components in the sixthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example.

The optical data of the sixth example of the optical imaging lens setare shown in FIG. 32 while the aspheric surface data are shown in FIG.33. TTL is 5.896 mm. Fno is 1.73. The image height is 3.5 mm. HFOV is37.047 degrees. T₅min (98, 89) is 0.464 mm. In particular, 1) the TTL ofthe sixth example is shorter than that of the first example of thepresent invention, 2) the HFOV of the sixth example is better than thatof the first example of the present invention, and 3) the Fno of thesixth example is better than that of the first example of the presentinvention and the yield would be better.

Seventh Example

Please refer to FIG. 18 which illustrates the seventh example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 19A for the longitudinal spherical aberration on the image plane 71of the seventh example; please refer to FIG. 19B for the astigmaticaberration on the sagittal direction; please refer to FIG. 19C for theastigmatic aberration on the tangential direction, and please refer toFIG. 19D for the distortion aberration. The components in the seventhexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example.

The optical data of the seventh example of the optical imaging lens setare shown in FIG. 34 while the aspheric surface data are shown in FIG.35. TTL is 5.862 mm. Fno is 1.76. The image height is 3.5 mm. HFOV is36.447 degrees. T₅min (77, 73) is 0.282 mm. In particular, 1) the TTL ofthe seventh example is shorter than that of the first example of thepresent invention, 2) the HFOV of the seventh example is better thanthat of the first example of the present invention, and 3) the Fno ofthe seventh example is better than that of the first example of thepresent invention.

Eighth Example

Please refer to FIG. 20 which illustrates the eighth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 21A for the longitudinal spherical aberration on the image plane 71of the eighth example; please refer to FIG. 21B for the astigmaticaberration on the sagittal direction; please refer to FIG. 21C for theastigmatic aberration on the tangential direction, and please refer toFIG. 21D for the distortion aberration. The components in the eighthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example.

The optical data of the eighth example of the optical imaging lens setare shown in FIG. 36 while the aspheric surface data are shown in FIG.37. TTL is 5.911 mm. Fno is 1.73. The image height is 3.5 mm. HFOV is37.088 degrees. T₅min (95, 87) is 0.397 mm. In particular, 1) the TTL ofthe eighth example is shorter than that of the first example of thepresent invention, 2) the HFOV of the eighth example is better than thatof the first example of the present invention, and 3) the Fno of theeighth example is better than that of the first example of the presentinvention.

Some important ratios in each example are shown in FIG. 38. The distancebetween the sixth image-side surface 62 of the sixth lens element 60 tothe filter 70 along the optical axis 4 is G6F; the thickness of thefilter 70 along the optical axis 4 is TF; the distance between thefilter 70 to the image plane 71 along the optical axis 4 is GFP; thedistance between the sixth image-side surface 62 of the sixth lenselement 60 to the image plane 71 along the optical axis 4 is BFL.Therefore, BFL=G6F+TF+GFP.

In the light of the above examples, the inventors observe at least thefollowing features:

1. The first object-side surface of the first lens element with a convexportion in a vicinity of the optical axis helps concentrate the lighteffectively.2. The second lens element has an image-side surface with a concaveportion in a vicinity of its periphery. The sixth lens element has animage-side surface with a convex portion in a vicinity of its periphery.The above arrangements collectively reduce the aberration of the opticalimaging lens set, and eliminate the curvature of field and thedistortion to maintain a good imaging quality. In addition, the abovecurvatures to go with the limitation of T₅min/T₅≦0.6 effectively improvethe imaging quality. Preferably, the image-side surface of the fifthlens element with a convex portion in a vicinity of the optical axishelps the correction of the aberration.

In addition, the inventors discover that there are some better ratioranges for different data according to the above various importantratios. Better ratio ranges help the designers to design a betteroptical performance and an effectively reduce length of a practicallypossible optical imaging lens set. For example:

1. ALT/(G₃₄+G₅₆)≦17.5. Preferably, the ratio may be 3.7˜17.5.2. EFL/T₃≦18.5. Preferably, the ratio may be 6.7˜18.5.3. T₅/T₄≦3.5. Preferably, the ratio may be 1.0˜3.5.4. ALT/T₂≦13.5. Preferably, the ratio may be 9.5˜13.5.5. AAG/T₃≧1.8. Preferably, the ratio may be 1.8˜6.3.6. EFL/(G₁₂+G₂₃)≦13.0. Preferably, the ratio may be 6.5˜13.0.7. T₁/T₂≦3.6. Preferably, the ratio may be 2.3˜3.6.8. (G₂₃+G₄₅)/T₂≦4.0. Preferably, the ratio may be 2.0˜4.0.9. T₅/(G₃₄+G₄₅)≦3.5. Preferably, the ratio may be 0.6˜3.5.10. ALT/(T₂+T₆)≦4.4. Preferably, the ratio may be 3.2˜4.4.11. EFL/(T₃+T₆)≦6.5. Preferably, the ratio may be 3.6˜6.5.12. AAG/(T₂+T₃)≦3.5. Preferably, the ratio may be 1.2˜3.5.13. T₁/T₃≧1.0. Preferably, the ratio may be 1.0˜3.1.14. (G₂₃+G₅₆)/T₂≦3.6. Preferably, the ratio may be 2.0˜3.6.15. EFL/(T₄+T₆)≦5.7. Preferably, the ratio may be 4.3˜5.7.16. ALT/(G₂₃+G₃₄)≦8.0. Preferably, the ratio may be 4.3˜8.0.17. EFL/(T₁+T₃)≦5.0. Preferably, the ratio may be 3.2˜5.0.18. T₅/(G₁₂+G₂₃)≦1.8. Preferably, the ratio may be 1.1˜1.8.

The above adjustments take the easiness of the fabrication intoconsideration so at the same time they have the benefits of high yield.

In the light of the unpredictability of the optical imaging lens set,the present invention suggests the above principles. The abovelimitations may be properly combined at the discretion of persons whopractice the present invention and they are not limited as shown above.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical imaging lens set, from an object sidetoward an image side in order along an optical axis comprising: a firstlens element, a second lens element, a third lens element, a fourth lenselement, a fifth lens element and a sixth lens element, said first lenselement to said sixth lens element each having an object-side surfacefacing toward the object side as well as an image-side surface facingtoward the image side, wherein: said first lens element has anobject-side surface with a convex portion in a vicinity of the opticalaxis; said second lens element an image-side surface with a concaveportion in a vicinity of its periphery; said sixth lens element has animage-side surface with a convex portion in a vicinity of its periphery,the optical imaging lens set exclusively has six lens elements withrefractive power, T₅min is the minimal distance from the object-sidesurface of said fifth lens element to the image-side surface of saidfifth lens element and said fifth lens element has a fifth lens elementthickness T₅ along the optical axis to satisfy T₅min/T₅≦0.6.
 2. Theoptical imaging lens set of claim 1, wherein ALT is the total thicknessof all six lens elements, an air gap G₃₄ between said third lens elementand said fourth lens element along said optical axis and an air gap G₅₆between said fifth lens element and said sixth lens element along saidoptical axis to satisfy ALT/(G₃₄+G₅₆)≦17.5.
 3. The optical imaging lensset of claim 1, wherein EFL is the effective focal length of the opticalimaging lens set and the third lens element has a third lens elementthickness T₃ along the optical axis to satisfy EFL/T₃≦18.5.
 4. Theoptical imaging lens set of claim 1, wherein the fourth lens element hasa fourth lens element thickness T₄ along the optical axis to satisfyT₅/T₄≦3.5.
 5. The optical imaging lens set of claim 1, wherein ALT isthe total thickness of all six lens elements and the second lens elementhas a second lens element thickness T₂ along the optical axis to satisfyALT/T₂≦13.5.
 6. The optical imaging lens set of claim 1, wherein thethird lens element has a third lens element thickness T₃ along theoptical axis and the sum of all air gaps AAG between each lens elementsfrom said first lens element to said sixth lens element along theoptical axis to satisfy AAG/T₃≧1.8.
 7. The optical imaging lens set ofclaim 1, wherein EFL is the effective focal length of the opticalimaging lens set, an air gap G₁₂ between said first lens element andsaid second lens element along said optical axis and an air gap G₂₃between said second lens element and said third lens element along saidoptical axis to satisfy EFL/(G₁₂+G₂₃)≦13.
 8. The optical imaging lensset of claim 1, wherein the first lens element has a first lens elementthickness T₁ along the optical axis and the second lens element has asecond lens element thickness T₂ along the optical axis to satisfyT₁/T₂≦3.6.
 9. The optical imaging lens set of claim 1, wherein thesecond lens element has a second lens element thickness T₂ along theoptical axis, an air gap G₂₃ between said second lens element and saidthird lens element along said optical axis and an air gap G₄₅ betweensaid fourth lens element and said fifth lens element along said opticalaxis to satisfy (G₂₃+G₄₅)/T₂≦4.
 10. The optical imaging lens set ofclaim 1, wherein an air gap G₃₄ between said third lens element and saidfourth lens element along said optical axis and an air gap G₄₅ betweensaid fourth lens element and said fifth lens element along said opticalaxis to satisfy T₅/(G₃₄+G₄₅)≦3.5.
 11. The optical imaging lens set ofclaim 1, wherein ALT is the total thickness of all six lens elements,the second lens element has a second lens element thickness T₂ along theoptical axis and the sixth lens element has a sixth lens elementthickness T₆ along the optical axis to satisfy ALT/(T₂+T₆)≦4.4.
 12. Theoptical imaging lens set of claim 1, wherein EFL is the effective focallength of the optical imaging lens set, the third lens element has athird lens element thickness T₃ along the optical axis and the sixthlens element has a sixth lens element thickness T₆ along the opticalaxis to satisfy EFL/(T₃+T₆)≦6.5.
 13. The optical imaging lens set ofclaim 1, wherein said fifth lens element has an image-side surface witha convex portion in a vicinity of said optical axis.
 14. The opticalimaging lens set of claim 1, wherein the second lens element has asecond lens element thickness T₂ along the optical axis, the third lenselement has a third lens element thickness T₃ along the optical axis andthe sum of all air gaps AAG between each lens elements from said firstlens element to said sixth lens element along the optical axis tosatisfy AAG/(T₂+T₃)≦3.5.
 15. The optical imaging lens set of claim 1,wherein the first lens element has a first lens element thickness T₁along the optical axis and the third lens element has a third lenselement thickness T₃ along the optical axis to satisfy T₁/T₃≧1.
 16. Theoptical imaging lens set of claim 1, wherein an air gap G₂₃ between saidsecond lens element and said third lens element along said optical axis,an air gap G₅₆ between said fifth lens element and said sixth lenselement along said optical axis and the second lens element has a secondlens element thickness T₂ along the optical axis to satisfy(G₂₃+G₅₆)/T₂≦3.6.
 17. The optical imaging lens set of claim 1, whereinEFL is the effective focal length of the optical imaging lens set, thefourth lens element has a fourth lens element thickness T₄ along theoptical axis and the sixth lens element has a sixth lens elementthickness T₆ along the optical axis to satisfy EFL/(T₄+T₆)≦5.7.
 18. Theoptical imaging lens set of claim 1, wherein ALT is the total thicknessof all six lens elements, an air gap G₂₃ between said second lenselement and said third lens element along said optical axis and an airgap G₃₄ between said third lens element and said fourth lens elementalong said optical axis to satisfy ALT/(G₂₃+G₃₄)≦8.
 19. The opticalimaging lens set of claim 1, wherein EFL is the effective focal lengthof the optical imaging lens set, the first lens element has a first lenselement thickness T₁ along the optical axis and the third lens elementhas a third lens element thickness T₃ along the optical axis to satisfyEFL/(T₁+T₃)≦5.
 20. The optical imaging lens set of claim 1, wherein anair gap G₁₂ between said first lens element and said second lens elementalong said optical axis and an air gap G₂₃ between said second lenselement and said third lens element along said optical axis to satisfyT₅/(G₁₂+G₂₃)≦1.8.